Generally, representative large-scale display apparatuses include liquid crystal displays (LCDs), plasma display panels (PDPs), etc.
Unlike self-luminous type PDPs, LCDs require a separate backlight unit because they cannot generate light by themselves.
Backlight units for use in LCDs are classified into edge type backlight units and direct type backlight units according to positions of light sources. In an edge type backlight unit, light sources are arranged at left and right edges or upper and lower edges of an LCD panel and a light guide plate is provided to uniformly distribute light throughout a surface of the LCD panel. Such an edge type backlight unit ensures uniform brightness and enables production of an extremely thin display panel.
A direct type backlight unit is generally applied to displays of 20 inches or more. The direct type backlight unit advantageously has greater light efficiency than the edge type backlight unit by virtue of a plurality of light sources arranged below a panel. Accordingly, such a direct type backlight unit is mainly used in a large-scale display requiring high brightness.
Conventional edge type or direct type backlight units use cold cathode fluorescent lamps (CCFL) as light sources thereof.
Such backlight units, which use CCFLs, however, have several disadvantages, such as consumption of a great quantity of electric power because voltage should always be applied to the CCFLs, low color reproduction efficiency (about 70% that of a cathode ray tube (CRT)), and environmental pollution caused by use of mercury.
Currently, research is being conducted into backlight units using light emitting diodes (LEDs) as a solution to the above described problems.
In the case of backlight units using LEDs, turning on or off a part of an LED array is possible, so that it may be possible to achieve remarkable reduction in power consumption. In particular, RGB LEDs exhibit color reproduction exceeding a color reproduction range of 100% specified by the National Television System Committee (NTSC) and can provide more vivid images to consumers.
Further, LEDs fabricated through semiconductor processes are environmentally friendly.
Although LCD products using LEDs having the above-mentioned advantages have been introduced, these LCD products require expensive drivers, PCBs, etc. because LEDs have a driving mechanism different from conventional CCFLs.
For this reason, LED backlight units are applied only to high-price LCD products at present.